# Polars 1.2.0 — Python Polars 1.2.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2024-07-16
- Version: 1.2.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.2.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.2.0

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **fixed** — Fix pathological performance issue in window-order-by
- **changed** — Cache path resolving of scan functions
- **changed** — Add fastpath for when rounding by single constant durations
- **changed** — Improve parallelism in writing hive parquet
- **changed** — Support datetime in predicate during hive partition pruning
- **changed** — Collect Parquet dictionary binary as view
- **added** — Add infer_schema parameter to read_csv / scan_csv
- **added** — Add option to include file path for Parquet, IPC, CSV scans
- **added** — Support describe on decimal
- **added** — Support use of SQLAlchemy Connectable in write_database
- **changed** — Expose returns_scalar to map_elements
- **added** — Hugging Face path expansion
- **fixed** — Support duplicate expression names when calling ufuncs
- **fixed** — Interpret %y consistently with Chrono in to_date/to_datetime/strptime
- **fixed** — Fix explode invalid check
- **fixed** — Expand brackets in async glob expansion
- **fixed** — Fix row index disappearing after projection pushdown in NDJSON
- **fixed** — Fix struct to enum is_in
- **fixed** — Method dt.truncate was sometimes returning incorrect results for pre-1970 datetimes
- **fixed** — Fix retries parameter in scan functions not taking effect when it was set to 0

##### 🚀 Performance improvements

- Fix pathological perf issue in window-order-by (#17650)
- Cache path resolving of `scan` functions (#17616)
- Add `ArrayChunks` to optimize codegen of BatchDecoder (#17632)
- Rechunk before we go into grouped gathers (#17623)
- Cache schema resolve back to DSL (#17610)
- Add fastpath for when rounding by single constant durations (#17580)
- Improve parallelism in writing hive parquet (#17512)
- Support datetime in predicate during hive partition pruning (#17545)
- Batch nested embed parquet decoding (#17549)
- Batch nested Parquet decoding (#17542)
- Collect Parquet dictionary binary as view (#17475)

##### ✨ Enhancements

- Hugging Face path expansion (#17665)
- Add DSL validation for cloud eligible check (#17287)
- Raise informative error message if non-IntoExpr is passed by name in \*Frame.group\_by (#17654)
- Add `infer_schema` parameter to `read_csv` / `scan_csv` (#17617)
- Change API for writing partitioned Parquet to reduce code duplication (#17586)
- Cache schema resolve back to DSL (#17610)
- Expose `returns_scalar` to map\_elements (#17613)
- Add option to include file path for Parquet, IPC, CSV scans (#17563)
- Support `describe` on decimal (#15092)
- Support datetime in predicate during hive partition pruning (#17545)
- Raise more informative error message for directories containing files with mixed extensions (#17480)
- Exclude empty files from directory/glob expansion (#17478)
- Support use of SQLAlchemy "Connectable" in `write_database` (#17470)

##### 🐞 Bug fixes

- Support duplicate expression names when calling ufuncs (#17641)
- Interpret %y consistently with Chrono in to\_date/to\_datetime/strptime (#17661)
- Fix explode invalid check (#17651)
- Raise for overlapping index/column names in pandas dataframes post string coercion (#17628)
- Expand brackets in async glob expansion (#17630)
- Fix row index disappearing after projection pushdown in NDJSON (#17631)
- Fix struct -> enum is\_in (#17622)
- Don't needlessly unwrap in `pivot_schema` (#17611)
- Reject literal input in `sort_by_exprs()` (#17606)
- Don't enforce row order in join test results where not guaranteed (#17596)
- Bitmap collect into safety (#17588)
- Make schema picklable (#17524)
- Handle current position of file objects (#17543)
- Set `O_CLOEXEC` on duplicated file descriptor (#17537)
- Method dt.truncate was sometimes returning incorrect results for pre-1970 datetimes (#17582)
- Defer path expansion until `collect` in file scan methods (#17532)
- Fix `retries` parameter in scan functions not taking effect when it was set to `0` (#17564)
- Don't unwrap send attempt to oneshot channel (#17566)
- Fix scanning from HTTP cloud paths (#17571)
- Properly implement struct (#17522)
- Add right to lazyframe join docstring (#17529)
- Fix predicate pushdown for `.list.(get|gather)` (#17511)
- Make sure `scan_ipc` does not go through fsspec (#17495)
- Turn panic into error when serializing Object types (#17353)
- Fix struct expansion and raise on exclude (#17489)
- Normalize path in `sink_csv` (#17476)

##### 📖 Documentation

- Update `plot` docs to refer to docstrings (#17504)
- Rename `str.lengths` to `str.len_bytes` in description text (#11577) (#17626)
- Create example for `polars.Expr.bin.decode` (#17508)
- Add right join in the user guide (#17608)
- Adjust rendering of links in `read_database_uri` docstring (#17536)
- Update SQL examples in README (#17568)
- Fixup "deprecated" directive for `DataFrame.melt` and `LazyFrame.melt` (#17530)
- Add `write_parquet_partitioned` (#17488)
- Add example for writing hive partitioned parquet to user guide (#17483)
- Fix typo in Getting Started section of user guide (#17465)

##### 🛠️ Other improvements

- Add DSL validation for cloud eligible check (#17287)
- Add `ArrayChunks` to optimize codegen of BatchDecoder (#17632)
- Move path logic to from `utils` to `path_utils` in polars-io (#17635)
- Fix struct gather (#17621)
- Back to StructChunked name (#17609)
- Remove unused

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.2.0]_